Cast disk for turbine rotors



Aug. 16, 1949- .v. CRONSTEDT v CAST DISK FOR TURBINE ROTORS 2'Sheets-Sheet 1 Filed Nov. 6, 1944 Aug.- 16, 1949,

v. CRONSTEDT 2,479,039 CAST DISK FOR TURBINE ROTORS -Fi1ed Nov. 6, 19442 Sheets-Sheet 2' FIG. 2

|N V TOR although the disk need Patented Aug. 16, 1949 2,479,039 CASTDISK Foa TURBINE morons Val Cronstedt, Marlboro,

Conn, assignor to United Aircraft Corporation, East Hartford, Coma, acorporation of Application November 6, 1944, Serial N 0. 562,252 2Claims. (Cl. 253-39) This invention relates to the manufacture of thedisks from which the turbine rotor is made.

Multi-stage turbine rotors have been made up of a shaft having integraldisks to the peripheries of which rows of blades are fastened, generallyby blade fastenings which hold the blades individually .on the disk.Since each blade must be separately made and separately placed on therotor, the blading of the rotor is an expensive process. A feature ofthe invention is aturbine disk having blades cast integrally with theremainder of the disk.

Where the turbine operates at extremely high temperatures it isdesirable to have the blades made of a different material from theremainder of the disks. For example, the blade is preferably of amaterial which is extremely heat resistant, not be as heat resistant,but should have substantial ductility to withstand the high stresses. Afeature of the invention is the manufacture of a turbine disk having theblade material difierent from that of the remainder of the disk and withthe blades and disks all made in one piece. This may be accomplished byfirst pouring the blade material into the centrifugal mold and then,while this material is still molten, pouring the disk material.

A feature of the invention is the centrifugal casting of the disk, andintegral blades to provide the desired-characteristics in the materialof the blades and disk, and also to obtain a satisfactory surface finishon the blades. Another feature is the use of an investment for'at leasta part of the mold in which the casting is made, thereby producing thedesired blade shape and permitting the casting of the disk and bladeswithin said tolerances.

Other objects and advantages will be apparent from the specification andclaims, and from the accompanying drawings which illustrate anembodiment of the invention.

Fig. 1 is a sectional view through the rotor disk.

Fig. 2 is a sectional view through the mold in 'which the disk is cast.

Fig. 3 is a fragmentary sectional view at right angles to the sectionalview of Fig. 1.

The turbine disk may form one of a number of disks positioned in end toend relation in forming the rotor for a multi-stage turbine, one exampleof which is shown in the copending application of Soderberg, Serial No.550,899, filed August 23-, 1944, which issued on February 8, 1949 asPatent No. 2,461,242. As shown the rotor disk includes an annular bladesupporting portion ID from the periphery of which the blades l2 extend.Shrouds Delaware Il may connect the tips of the blades together,preferably in groups of blades. The central portion I0 may. as shown, bea formed disk to withstand the stress applied to the disk and may havelateral flanges l6 and I8 which are engaged with similar flanges on theadjoining disks which make up the completed rotor.

The blades are cast integrally with the rotor, thereby eliminating anyjunction either in the form of blade fastenings or welded attachment ofthe blades to the disk. As shown, the disk or hub Ill has a central hubis which may be of a material particularly adapted for the disk such asa high-stress material and theblades may be of a different materialsuitable for turbine blades, such as a castable heat-resistant material,there being an annular ring 20 between the central hub and the bladesand integral with both the hub and blades where the ring and hub areintegrally connected, there is a narrow band 2| in which the materialsmutually alloy and form a gradation from the blade and ring material tothe hub material. It will be understood that the materials of both huband blades may be selected from heat resistant alloys generally .of thenonferrous type known to be suitable for these purposes.

With reference to. Fig. 2, the disk may be made by casting it in asingle piece in a mold 22. For best results, the part of the mold inwhich the blades are formed may be a core 24 made of investment materialwhich can be baked dry and hard at an elevated temperature and whichwill impart to the blades the desired surface finish and will permit theblades to be formed within the desired tolerances and dimensions. Thedrag 28 and cope 28 of the mold in the arrangement shown may be eitherconventional in the mold of material or may, if desired, also be made ofan investment material which may be the same as that of the core 24.

The core is formed by placing blade patterns in position in the core boxand thereafter placing the investment material around the inserts. Theinvestment is hardened and the inserts are removed, either by withdrawalif the contour of the blades permits, or by melting the inserts out.Risers 30 and 32 in the form of rings may be provided adjacent theperipheries of the end of the blade being connected to the blades bypassages 34 formed in the mold. These risers permit the discharge fromthe casting of any impurities that may have been picked up by thematerial as it is poured into the opening in the mold. When the mold isassembled an end opening 36 is formed between the cope and the drag andwithin the core 24 which corresponds in shape to the desired roughdimension of the disk, the

parts of the mold being clamped between platescentrifugal forcedeveloped by the mold rotationfills the openings in the core to produceblades of the desired contour.

The cast disk may be entirely of one material in which case enough ofthe desired material is introduced into the mold in one operation. Itmay be advantageous, however, to introduce into the mold firstsufilcient blade material to fill the spaces within the core 20 and ashort distance toward the center of the mold from the core to form theblades and the ring l9 integral therewith and, thereafter, to pour intothe mold, hub material enough to fill the remainder ofthe space in themold. It is desirous to have the first of the hub material poured injust as the last of the blade material is being poured, thereby causingthe small amount of alloying of the materials and giving the small areaor band IQ of mutually alloyed materials, as shown in Fig. 1.

After the disk has been cast and the mold and investment material areremoved from the disk the hub and ring portions of the disk may then bemachined to the desired contours and dimensions of the disk of Fig. 1.

It is to be understood that the invention is not limited to the specificembodiment herein illustrated and described, but may be used in otherways without departure from its spirit as defined by the followingclaims.

I claim: 1. A cast one piece disc for a turbine rotor havrotor disk ispreferably the plates 38 and A in v through opening 46 and l ing acentral hub of cast high-stress material, a surrounding ring of a castheat-resistant material of different composition than the highstressmaterial of the hub, said ring being integral with, and located at andextending radially from, the periphery of the hub, and blades extendingfrom the periphery of the ring and integral therewith, said blades beingformed of the same cast heat-resistant material as the rin and said ringhaving its periphery continuous.

2. A cast one piece disc for a turbine rotor having a central hub ofcast high-stress material, a surrounding ring, of a cast heat-resistantmaterial of different composition than the high-stress material of thehub, said ring being integral with, and located at and extendingradially from, the periphery of the hub, and blades extending from theperiphery of the ring and integral therewith, said blades being formedof the same cast heatresistant material as the ring, said ring havingits periphery continuous, and a cast joint integrally connecting saidring and hub together, said joint consisting of an alloying of saidhighstress and heat-resistant materials.

VAL CRONSTEDT.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 550,948 Croft Dec. 10, 1895839,560 Davis Dec. 25, 1906 901,459 MacDonald Oct. 20, 1908 901,960Farquhar Oct. 27, 1908 1,008,478 Hopson et a1. Nov. 14, 1911 1,546,011De Bats July 14,1925 1,943,720 Campbell Jan. 16, 1934 2,058,479 LysholmOct. 27, 1936 2,079,473 Wade May 4, 1937 2,200,287 Lysholm May 14, 19402,270,822 McCarroll et al Jan. 20, 1942 2,299,860 Stoody et al. Oct. 27,1942

